1. Field
One embodiment of the invention relates to an exchange system formed as a private branch telephone system, a button telephone set, and an exchange.
2. Description of the Related Art
An existing exchange system has a function of notifying an operator the fact that a failure has occurred in the system. Its representative methods are as follows:                (1) An exchange and a circuit board are provided with light emitted diodes (LEDs) to light the LEDs or blink them in the occurrence of the failure        (2) The failure information is notified to network management equipment via a local area network (LAN)        (3) An e-mail notifying the occurrence of the failure is sent to a prescribed e-mail address via the LAN        (4) The failure is notified to the operator by making a call to a prescribed telephone number via a public telephone line.        
The method described in the above (1) is effective in shortening a time of maintenance work for replacing the circuit board with the failure and checking a line. The methods described in the above (2)-(4) are utilized for the purpose of remote maintenance and centralized managements and effective in shortening a time from an occurrence of a failure up to a start of maintenance work. As described above, the existing system fully prepares a failure notification function to the operator.
In contrast, the existing system does not fully prepare a function of notifying the occurrence of the failure to a user of a telephone terminal. Although a solution of this defect has been exemplified in Japanese Patent Application KOKAI Publication No. 7-95638, even the exemplified technique cannot notify the occurrence of the failure to the user immediately. Furthermore, in the case of absence of the network management equipment in a small scale office, etc., and under an environment in which any external connection via the LAN is not established, a failure notification is not put into practice appropriately. As mentioned above, each existing exchange system does not have an enough failure notification function to the user and desires to do something therefore.